Millions of tons of debris from the Japanese earthquake and tsunami in March is headed for the West Coast of the US.

A Russian ship has spotted a floating island of junk passing the Midway Islands northwest of Hawaii - some 2,000 miles from the source of the tsunami.

And computer models from the University of Hawaii suggest it's due to hit the US mainland in the next three years.

"Yesterday, i.e. on September 22, in position 31042,21 N and 174045,21 E, we picked up on board the Japanese fishing boat. Radioactivity level – normal, we’ve measured it with the Geiger counter," reported Natalia Borodina, information and education mate of the Pallada.

"At the approaches to the mentioned position (maybe 10 – 15 minutes before) we also sighted a TV set, fridge and a couple of other home appliances."

Subsequent observations found fragments of houses, along with items from drums to boots.

"On October 8, the Pallada entered the port of Vladivostok, and Borodina was able to send pictures," says the STS Pallada in a statement.

"The most remarkable one is of a small fishing vessel about 20 feet long, which they were able to hoist up onto the Pallada. The markings on the wheel house of the boat show its home port to be in the Fukushima Prefecture, the area hardest hit by the tsunami."

The debris was found exactly where predicted by the University of Hawaii's International Pacific Research Center (IPRC) computer models - although it got there a little faster than expected.

It's expected to first make landfall in the Windward Islands sometime in December. What fails to wash up there will head onwards to the main Hawaiian Islands and the North American West Coast.

Altogether, there's believed to be as much as 20 million tons of debris on its way.